Apparatus for the noninvasive determination and acoustical representation of the dynamic behavior of peripheral venous hemodynamic

ABSTRACT

A measuring apparatus for the noninvasive determination of peripheral outflow and flow disturbances in the extremities of human beings includes at least one light transmitter for directing light onto the skin of the subject under test and at least one light receiver for receiving reflected radiation and an evaluation and read-out circuit for ascertaining the temporal course of the blood outflow or inflow in the veins by measuring the changes in light reflection. The evaluation and read-out circuit is provided with a digitally controlled tone generator and an electroacoustic transducer that emits a first signal to indicate readiness of the apparatus to effect measurement, a second succession of tones, the frequency of which follows the changes in the intensity of the light reflection until termination of the blood outflow or inflow, and a third signal which indicates the end of the measuring.

CROSS-REFERENCE TO RELATED APPLICATIONS

The subject matter of the present application is related to thatdisclosed in applicant's co-pending and commonly owned U.S. patentapplication Ser. No. 07/026,607, filed 3/17/87 and entitled"Microprocessor Controlled Apparatus for the Noninvasive Determinationof Peripheral Outflow and Flow Disturbances," the disclosure of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a measuring apparatus for thenoninvasive determination of peripheral blood outflow and flowdisturbances in the extremities of human beings. Measuring devices ofthis type are disclosed in, by way of illustration, German Patent No. 3100 610.8 or German Patent No. 33 18 746.0. In the measuring devicedisclosed in DE-PS No. 31 00 610.8, the temporal course of the reflectedor dispersed back part of the radiation is evaluated in an analog mannerand recorded by means of a recording device. In the measuring devicedisclosed in DE-PS No. 33 18 746.0, the analog signal is translated orconverted into a digital signal by means of a transmission-receptiondata connection point circuit and transferred to a calculator device.The calculator device calculates the physical rating parameters for theanalog light reflection curves. This measuring device is, accordingly,particularly suitable for conducting and evaluating a test series.

Both prior art measuring devices share the drawback that they cannoteasily be constructed as handy, portable apparatuses: neither therecording device described in DE-PS No. 31 00 610.8 nor the commonmicro-computer with floppy disk drives, etc. described in DE-PS No. 3318 746.0 can be miniaturized to the extent that they can be readilyfabricated into a portable apparatus. Moreover, the power consumption ofthe prior art measuring devices is too great for portable apparatuses.

It is especially disadvantageous with regard to the prior art measuringdevices that the operating staff determines the commencement and thetermination of each measurement, thereby making subjective measurementerrors possible.

SUMMARY OF THE INVENTION

In view of the above, it is an object of the present invention, amongothers, to provide a measuring apparatus for the noninvasivedetermination of peripheral outflow and flow disturbances in theextremities of human beings, which can also be constructed as aportable, hand-held apparatus.

The present invention is based on the fundamental idea that theevaluation circuit is provided with a digitally controlled tonegenerator and the read-out of the measuring results is provided by meansof an electro-acoustic transducer. In this manner, it is possible toconstruct the measuring apparatus of the present invention as a compactand light-weight apparatus having low-power consumption requirements.The physician can easily carry the apparatus of the present inventionaround with him, by way of example, during an activity program in whichphysical exercises, etc. are performed and is able with little effort toexamine the inflow or outflow of the veins immediately following theexercises, whereby the evaluation and read-out circuit emits a firstsignal which, by way of illustration, is an optical attention-attractingsignal or, more preferably, an audible sound indicating to the examiningindividual that the apparatus is ready to measure and also provide avalue representative of constant quiescent blood circulation of theskin. The actual measuring result, i.e., the measured light reflectionis represented by a second succession of audible tones, the frequency ofwhich follows the change in intensity of the light reflection, e.g., asa result of leg movements, until the blood outflow or inflow terminates.The end of the measurement, i.e., the return of a constant skincirculation following the executed movement, is indicated by a thirdsignal, again preferably by a third audible tone or by a thirdsuccession of tones or even, for example, the end of the tone.

The acoustical read-out of the measuring results makes it possible forthe examining individual to analyze the outflow or inflow of the veinsor arteries and to detect abnormal changes, etc. with unexpectedreliability.

It is, moreover, possible to use the tone generator and theelectro-acoustic transducer, e.g., a loudspeaker, provided according tothe invention, to support the activity program of the examiningindividual, by way of example, by means of a rhythmic succession oftones. Of course, it is possible to select from different successions oftones to support different activity programs.

The apparatus of the present invention can, by way of illustration,calibrate itself, whereby energy applied to the light transmitter ortransmitters is continuously raised until the signal measured by thelight receiver or receivers has attained a specific signal-to-noiseinterval. The first tone, indicating the commencement of readiness tomeasure, can then be emitted following termination of theself-calibration cycle.

The apparatus of the present invention can, of course, also be providedwith a memory as well as a data output port. The measurement results canbe stored in the memory and subsequently be transferred to anotherevaluation instrument. Naturally, it is also possible to transfer themeasurement results and/or evaluation results during the measuring via adata line to another evaluation instrument, by way of illustration, amicrocomputer or a printer.

The present invention provides a measuring apparatus for the noninvasivedetermination of peripheral outflow and flow disturbances in theextremities of human beings, having at least one light transmitter fordirecting light onto the skin of a human being and one light receiverfor sensing light reflected therefrom as well as an evaluation andread-out circuit to ascertain the temporal course of the blood outflowor inflow in the veins by measuring the changes in light reflection. Theinvented apparatus distinguishes itself in that the evaluation andread-out circuit is provided with a digitally controlled tone generatorand an electroacoustic transducer and emits a first signal to indicatereadiness of the apparatus to effect measurement; a second succession oftones, the frequency of which follows the changes in the intensity ofthe light reflection until termination of the blood outflow or inflow;and a third signal which indicates the end of the measuring sequence.

Other objects and further scope of applicability of the presentinvention will become apparent from the detailed description to follow,taken in conjunction with the accompanying drawings, in which like partsare designated by like reference characters.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 illustrates an apparatus in accordance with the present inventionin schematic form connected to a human subject;

FIG. 2 depicts a block diagram of an evaluation and read-out circuit inaccordance with the present invention;

FIGS. 3a and 3b illustrate a representation of the measurement resultsselected in accordance with the present invention;

FIGS. 4a and 4b illustrate the read-out of the acoustical representationof FIG. 3;

FIG. 5 illustrate an additional variation of the acousticalrepresentation of FIGS. 4a and 4b.

DESCRIPTION OF THE PREFERRED EMBODIMENT

As shown in schematic form in FIG. 1, a measuring apparatus 1 inaccordance with the present invention is constructed as a small,portable apparatus. The measuring apparatus 1 is provided with anelectro-acoustic transducer 3, by way of illustration, a loudspeaker, aLCD display unit 4, a plug 5 for an optical measuring head 2 having oneor several light transmitters and receivers, which can be placed on theextremities of human beings, a plug 6 for earphones, as well as a plug 7for connection to a stationary evaluation instrument to transfer datafrom the measuring apparatus 1. An on/off switch 8, a function key 9 forselecting the various operations, and an indicator key 10 (e.g., for themenu guide) are also provided.

FIG. 2 shows a block diagram of the evaluation and read-out circuit inaccordance with the present invention, whereby the elements that are thesame as in FIG. 1 are designated with the same reference characters. Amicroprocessor 12, a drive unit 13 for the light transmitter of theoptical measuring head 2, and a receiver 14 for the light receiver ofthe optical measuring head 2 form an active control loop 11, whereby thedrive unit 13 and the receiver 14 may be arranged in a manner similar tothat disclosed in German Patent Nos. 31 00 610 and 33 18 746, thedisclosures of which are incorporated herein by reference.

FIGS. 3 to 5 illustrate the mode of operation of the measuring apparatus1 of FIGS. 1 and 2. FIG. 3a shows an example of a vein pressure curve,as it is obtained invasively by means of so-called phlebodynamometry. Inphase I, a constant blood circulation of the skin is obtained from aseated patient and, as shown, is an almost constant pressure P_(o). Inphase II, the patient performs movements. Accordingly, the pressuredrops from the value P_(o) to the pressure P_(m) characteristic of therespective state of the patient's blood vessels. Following terminationof the activity or movement phase, the pressure rises again in phase IIIto approximately the initial value P_(o). The time it takes for thepressure to rise again to the initial value P_(o) is also an indicationof the respective state of the patient's blood vessels.

As illustrated in detail, by way of example, in DE-PS No. 31 00 610, thelight reflection detected by the optical detection head 2 follows thepressure curve illustrated in FIG. 3a.

FIG. 3b illustrates the acoustical read-out obtained with a measuringapparatus in accordance with the present invention using the pressurecurve depicted in FIG. 3a. After the constant blood circulation in theskin of a seated patient is obtained and the self-calibration of themeasuring apparatus 1 has been achieved, an audio tone with a frequencyof f_(o), for example, 1000 Hz., is emitted for a period of, by way ofillustration, 10 seconds. Prior to the start of the first activityphase, the tone is briefly interrupted. These interruptions can be, byway of illustration, 1 or 2 seconds prior to the start of the firstactivity phase and are an indication to the examining individual thatthe activity program is beginning. In activity phase II, a tone isemitted during the time t_(b) the frequency of which decreasescorresponding to the drop in pressure from P_(o) to P_(m) from f_(o) tof_(m). Following termination of activity phase II, the frequency of theemitted tone is normed from the individual frequency f_(m) for eachperson examined to a standard frequency f_(n), whose value is, by way ofillustration, 250 Hz (f_(o) /4). This frequency is preferred because thehuman ear is best able to differentiate changes in frequency in thisfrequency range.

During the inflow phase III, the frequency rises from the value f_(n) tothe initial value f_(o). At the end of the inflow phase III, a tone ofconstant frequency is emitted during a period of, by way ofillustration, 10 seconds. Subsequently measurement is terminated.Termination of measurement is indicated to the examining individual andpreferably to the person being examined by the end of the tone.

Noninvasive measurement of dynamic behavior of peripheral venushemodynamics takes place as described in German Pat. No. 3,100,610. Inparticular, the measurement device comprises a sensor which is placed onthe skin of the subject in which a luminous diode serves as a lighttransmitter and a light receiver, e.g., a photo-sensitive dial.Reflected light is reflected by different layers of the subject's skinand received by the luminous diode. It is known in the art that thedegree of reflection of light is correlated with emptying and filling ofthe veins, as described in German Pat. No. 3,100,610. According to thepresent invention, the emitted signal from the photo-sensitive diode isamplified and transposed, e.g., by means of a microcomputer, into asignal the frequency of which is within the sound frequency range of theacoustic spectrum.

FIG. 4b shows the reading on the LCD display unit 4 during measurement,corresponding to FIG. 3b, so that a more detailed description of FIG. 4ais not necessary. At the start of measuring, display unit 4 containsinformation indicating that self-calibration is being conducted at thetime or how such time remains until the start of measuring.Subsequently, it indicates the number of tones still to be heard duringthe activity program and thereby the time remaining for the activityprogram. During the inflow phase it can, by way of illustration, displayin a quasi analog manner the current skin reflection by therepresentation of a graph-like bar. Following termination of the inflowphase, the display unit 4 indicates, after a brief analysis period,e.g., the time required for the inflow. Switching to various otherreading values ensues by means of the indicator key 10. In this manner,the display unit 4 supports, on the one hand, the acoustical resultread-out, and can, on the other hand, be used for an interactivedialogue with the menu guide.

FIG. 5 shows another embodiment of the acoustical read-out of themeasuring results in accordance with the present invention. In thisembodiment, the person being examined is guided, during the activityphase, by the succession of tones emitted via the loudspeaker 3, wherebythe tones can, by way of illustration, vary over an octave. The start ofthe inflow phase is indicated by the change in the tone by two octavesto lower frequencies, whereby the start tone f_(o) preferably lies againat 1000 Hz. The inflow phase is again indicated by a change in pitch ofthe emitted tone.

Hereinbefore the present invention has been described in connection withpreferred embodiments of the invention. Naturally, the most diversemodifications are possible within the scope of the inventive idea. Byway of illustration, it is possible to guide the patient acousticallyvia the loudspeaker unit 3 while blood inflow or outflow is indicated tothe examining individual by means of earphones. The frequency of theproduced tones can, of course, also shift counter to the change indetected pressure. Furthermore, it is possible with the aid of theindicator key 10 to read-out other calculated parameters from themeasured and stored measurement data following the termination of eachmeasurement. With the aid of the function key 9 the following programpackages can, by way of example, be selected from the program memory ofthe microcomputer 12: a standard measurement program, a data read-outprogram, and a learning and training program for the operating staff.

Thus it will be appreciated from the above that as a result of thepresent invention, a highly effective apparatus for the noninvasivedetermination and acoustical representation of the dynamic behavior ofperipheral venous hemodynamic is provided by which the principalobjective, among others, is completely fulfilled. It will be equallyapparent and is contemplated that modification and/or changes may bemade in the illustrated embodiment without departure from the invention.Accordingly, it is expressly intended that the foregoing description andaccompanying drawings are illustrative of preferred embodiments only,not limiting, and that the true spirit and scope of the presentinvention will be determined by reference to the appended claims andtheir legal equivalent.

What is claimed is:
 1. A measuring apparatus for the noninvasivedetermination of peripheral outflow and flow disturbances in theextremities of human beings, having at least one light transmitter andone light receiver as well as an evaluation and read-out unit toascertain the temporal course of the outflow and inflow of blood in theveins by means of measuring the change in light reflection, whereby saidevaluation and read-out circuit is provided with a digitally controlledtone generator and an electroacoustic transducer for emitting a firstsignal to indicate that the apparatus is ready to measure, a secondsuccession of tones, the frequency of which follows the changes in theintensity of the light reflection until termination of blood outflow orinflow, and a third signal, which indicates the end of the measurement.2. An apparatus according to claim 1, whereby the first and third signalare acoustic signals.
 3. An apparatus according to claim 1, whereby thetone generator emits another succession of tones between the first toneand the second succession of tones to support an activity program.
 4. Anapparatus according to claim 1, whereby an additional succession ofshort impulses is integrated in the second succession of tones in orderto improve the time information.
 5. An apparatus according to claim 1,whereby said apparatus calibrates itself before commencing to measureand the tone generator emits the first tone after termination of saidself-calibration.
 6. An apparatus according to claim 1, whereby saidapparatus is provided with a memory to store the measured resultsdigitally.